(Note: All resubmission updates in this proposal are designated by italics) This Small Business Innovation Research (SBIR) Phase II project is an evaluation of a novel device designed to reduce the risk of surgical site infection, the Air Barrier System, during a pilot clinical trial. The Air Barrier System, shown during SBIR Phase I study to reduce the presence of colony forming units at an incision site by approximately 84%, shields surgical wounds with a localized high-purity air field. Multiple studies have shown that the primary source of surgical site bacterial colonization is Staphylococci shed from the skin of people present in the surgical theatre. The ability to prevent airborne precipitation of bacteria into the surgical site is an important factor in reducing postoperative infection, particularly in procedures incorporating prostheses. To execute this project, Nimbic Systems has formed a consortium with researchers and surgeons at Baylor College of Medicine / DeBakey Veterans Affairs Medical Center in Houston, TX. The VAMC is an ideal institution in which to conduct this research since it performs a broad range of surgical services, the incidence of surgical site infection in the targeted procedures exceeds 6%, and patient follow-up compliance is high. The primary objective of the Phase II research is to evaluate the ABS performance in a prospective randomized, double-blind pilot trial expanded to 300 surgical cases. Prosthesis implantation procedures, presenting high infection risk, in orthopedics (total hip arthroplasty), neurosurgery (lumbar laminectomy with instrumented fusion), and vascular surgery (femoral-popliteal bypass grafting) have been selected for study. The project's aims are to: (1) determine ABS effectiveness at reducing CFU contamination in a range of surgical specialties conducted by multiple surgical staff, (2) compare ABS performance against laminar airflow surgical environments, and (3) detect clinically relevant trends in SSI incidence between the control and experiment groups. Affirmative Phase II results will provide crucial data needed to begin commercialization of the Air Barrier System and to construct a pivotal prospective, randomized, multi-center clinical trial. The broader impact of this research is the potential reduction of surgical site infections after many types of procedures. Patients contracting an infection during high-risk procedures face considerable hardships, and evidence shows that elderly, less affluent, and non-urban populations are more likely to succumb to an SSI. The cost of treating surgical site infections developing after high-risk surgeries is greater than $2.6 billion annually and is projected to grow rapidly through the year 2030. The technology under development can potentially reduce cost to the healthcare system and prevent human suffering caused by such infections.